NIMSAWARD2025-abstracts

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P2-1584The development of superconducting conductors that can operate at 20 K is an urgent issue since helium is unevenly distributed resource and its price keeps rising. One of the candidates as a conductor is the MgB2superconductor with a Tcof 39 K. The use of Al as the sheath material for the conductors takes advantage of the light-weight property of MgB2. However, it requires a fabrication process below 660 ℃, which is the melting point (m.p.) of Al.Sintering under H2⚫does not promote the decomposition of MgB2or the formation of impurities ⚫reduces the sintering temperature and improves the Jcproperties of low-temperature sintered conductorsConclusionCharacterization of filling powdersCharacterization of tape samples⚫Fabrication of low-temperature sintered Al-sheathed conductors⚫Critical current measurement at 20 KFuture PlanIntroductionMgB2conductors are heat treated for either formation reaction (FP) of MgB2from starting materials such as Mg and B powders or sintering of MgB2powder at the final stage of the fabrication process. The FP normally occurs above 600 ℃ close to the m.p.of Al, which makes it difficult to use the Al sheath. When using commercial powders, the sintering temperature (Tsin) exceeds 900 ℃, but the Tsincan be reduced when using reactive powders.Theme underDiscussionSuperconducting System Group, GREEN Hiroki FUJIIE-mail：： FUJII.Hiroki@nims.go.jpDevelopment of low-temperature sintered MgB2conductorsKey Words: Low-temperature sintering, Light-weightPreparation of filling powder WC jar and ballsfillingmilled powderMgB2powderAr gas atmosphereAr gas atmosphereFe tubeball millingdeformationsintering @ 410–710 ℃Ar/H2gas atmospherepelletizedXRD patterns of sintered powdersFig. 1 XRD patterns of milled powders sintered at 530 ℃ under (i) Arand (ii) H2gas atmospheres and those at 680 ℃ under (iii) Arand (iv) H2. XRD peaks assigned to MgB2are indexed and those to WC are denoted by circles. The difference in sintering atmosphere does not promote the decomposition of MgB2or the formation of impurities.Microstructure of sintered tapes 2 m(a) Ar470(b) H4702 mFig. 2 SEM images of fractured surface of tapes sintered at 470 ℃ under (a) Arand (b) H2gas atmospheres.Heat treatment under H2gas atmosphere is effective in reducing the sintering temperature compared to Ar.Critical current density (Jc) propertyFig. 4 Jcat 4.2 K and 10 T of tapes sintered under Arand H2atmospheres as a function of Tsin. Fig. 3 Jc–Bproperties of tapes sintered at temperatures between 410 and 680 ℃ under Arand H2atmospheresUnder H2gas atmosphere, the Jcproperties can be improved even by low-temperature sintering.